<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
	div{
		width: 100px;
		height: 100px;
		border: 1px solid red;
	}
		#d1{
		position: absolute;        /*absolute:绝对定位*/
		top:0;
		left:0;
	}
</style>
</head>
<body>
	<div id="d1">div1</div>
	<div>div2</div>
</body>
</html>